1. Field of the Invention
The present invention relates to a film forming method and a film forming apparatus by which a film used for immersion exposure processing of performing exposure processing through a liquid is formed on a substrate such as a semiconductor substrate, and also relates to a pattern forming method that includes the above film forming method and forms a predetermined resist pattern on a substrate.
2. Description of the Background Art
In a manufacturing process of semiconductor devices, a photolithography technique is used for forming a circuit pattern on a semiconductor wafer. When the photolithography is used, the circuit pattern is formed through steps of forming a resist film (photoresist film) by applying a resist liquid over a semiconductor wafer, irradiating the resist film with light to expose the resist film corresponding to the circuit pattern, and then developing it.
Recently, there has been a tendency to increase packaging densities of semiconductor devices in view of improvement of operation speeds and others. In the photolithography technique, therefore, it has been required to miniaturize circuit patterns formed on semiconductor wafers. As a photolithography technique that achieves a high resolution of 45 nm node, there has been proposed immersion exposure, in which a liquid such as pure water having a higher refractivity than the air is supplied into a space between a wafer and an exposure projection lens employed, a wavelength of irradiation light passed through the projection lens is reduced owing to the refractivity of the liquid, and thereby a line width of the exposure is reduced (see International Laying-Open No. 2005-029559 brochure).
However, the immersion exposure processing is usually executed while forming a liquid current by supplying and drawing a liquid, and an air curtain is also formed in some cases. Therefore, a protective film (topcoat film) is applied over a film, e.g., a resist film formed on the wafer for protecting the resist film by preventing the resist film from being impregnated with the liquid and preventing elution of a resist ingredient from the resist film into the liquid. When edge portions of the protective film and others are not appropriately processed, the liquid current, the air current of the air curtain or the like may peel off the film from the wafer. When the film is peeled off, the peeled film changes into particles, which may contaminate an exposure device (e.g., the projection lens) and/or may cause a development defect.